1. Field of the Invention
The present invention is directed to expansion joints for high-pressure pipeline systems, and in particular, to methods and apparatus for monitoring pipeline expansion joint conditions, particularly in pressure-balanced expansion joints.
2. The Prior Art
When axial deflections exist in pipelines, expansion joints are required, in order to accommodate the changes in dimensions and/or relative positioning of pipeline components. One such environment for an expansion joint is in the exhaust from a turbine in a conventional fossil-fueled electric power generating plant.
One such type of expansion joint typically found in the just-mentioned environment is a pressure-balanced expansion joint (PBEXJ). A PBEXJ employs a first bellows (flow path bellows) to provide the fluid connection between two pipe ends. A second pair of bellows (balancing bellows) is concentrically arranged, to define an enclosed fluid space between them. The flow path bellows and the balancing bellows are typically arranged consecutively along the length of the expansion joint. The ends of the balancing bellows are mechanically connected to the pipe ends, so that separation of the pipe ends results in compression of the balancing bellows, while the flow path bellows extends. A flange plate surrounds one pipe end, but is movable relative to it. One end of the set of balancing bellows is attached to this first flange plate. The opposite end of the set of balancing bellows is affixed to the pipe end surrounded by the first flange plate, so that the balancing bellows encircle one pipe end and do not cross a gap between pipe ends. A second flange plate is affixed to the other pipe end, on the opposite side of the flow path bellows. Tie rods connect the two flange plates, so that when the pipe ends move apart, as the flow path bellows extends, the tie rods move the first flange plate relative to the pipe end it surrounds, causing the paired balancing bellows to be compressed. This results in a compression of whatever medium (air or other compressible fluid) is in the enclosed volume. This compression of the enclosed volume provides resistance to the extension movements of the flow path bellows, and acts as a damper, to smooth out pressure fluctuations and pressure-induced thrust forces that would tend to drive the pipe ends apart. Typically, a compression-limiting stop will be provided, to prevent overcompression of the flow path bellows, and likewise prevent overexpansion of the paired balancing bellows. By suitable selection of the diameters and effective cross-sectional areas of the various components, using known calculation skills available to one of ordinary skill in the art, the compression forces created in the balancing bellows, upon expansion of the flow path bellows, will counterbalance the expansion thrust, and cause the joint to stabilize at a particular position.
An advantage of such an expansion joint, is its ability to absorb externally imposed axial movement without imposing additional pressure loading on a system, so such joints are often used when additional pressure loading would be objectionable. The force resulting from the bellows in the expansion joint are not eliminated, but are typically not significant in comparison to the externally applied pressure thrusts that the joint is being used to accommodate. When a PBEXJ is used, forces that may change the length of the expansion joint will not be transferred to sensitive connections of the piping to the system.
The enclosed volume between the balancing bellows must be sealed, or substantially sealed, in order for the balancing bellows section to have significant damping effect, beyond the spring rates of the respective bellows. The medium that is used to fill the space typically has been air, or even the actual working medium. The latter is often an unfortunate choice, in that such media are often quite corrosive to the material of the bellows.
Prior art pressure-balanced expansion joints may be susceptible to variations in conditions in the various components that may affect the performance of the expansion joint. For example, drastic changes in temperature can affect the response of the enclosed volume in the balancing bellows to compression. In addition, thermally induced changes in dimension can effect the careful balancing of forces obtained by the particular structure.
It would be desirable to provide a method and apparatus for monitoring the conditions in a pipeline expansion joint, in particular a pressure-balanced expansion joint, in order to address changes in pipe line conditions, to alter the expansion joint""s ability to function in the face of such pipeline condition changes.
This and other desirable characteristics of the present invention will become apparent in light of the present specification, including claims, and drawings.
The present invention is directed, in part, to an apparatus for monitoring pipeline expansion joint conditions, for use with a pressure-balanced expansion joint of the type incorporating a flow path bellows connecting first and second pipe ends in fluid communication with one another and at least first and second balancing bellows defining a variable enclosed volume.
The apparatus comprises at least one sensor operably configured to sense and respond to environmental conditions existing within a pipeline fluid flow through a pressure-balanced expansion joint. The at least one sensor is further operably configured to generate a first signal corresponding to a particular value of at least one quantifiable characteristic of the environment existing within a pipeline fluid flow through a pressure-balanced expansion joint.
A control apparatus is operably connected to the sensor and configured to receive the first signal corresponding to a particular value of at least one quantifiable characteristic of the environment existing within a pipeline fluid flow through a pressure-balanced expansion joint.
The control apparatus is further operably configured to compare the first signal received from the sensor with numerical values stored in memory corresponding to various potential environmental conditions of a pipeline fluid flow through a pressure-balanced expansion joint and determine the environmental condition to which the received first signal corresponds.
The control apparatus is further operably configured, upon determination of the environmental condition to which the first signal corresponds, to generate a second signal.
The apparatus further comprises a source of compressible medium,
A flow control valve is operably connected to at least the source of compressible medium and the volume defined by first and second balancing bellows of a pressure-balanced expansion joint.
The flow control valve is further operable configured to have at least two operating positions, a first operating position preventing flow through the flow control valve, and a second operating position permitting flow between the source of compressible medium, and the volume defined by first and second balancing bellows of a pressure-balanced expansion joint.
The second signal is configured to direct the flow control valve to one of the at least two operating positions, depending upon the environmental condition to which the first signal corresponds, to, in turn, add compressible medium, remove compressible medium and/or maintain the mass of compressible medium within the defined volume.
The flow control valve may be provided with at least three positions, and the apparatus further comprises a fluid accumulator, operably connected to the flow control valve, the third operating position of the flow control valve permitting flow between the fluid accumulator and the volume defined by first and second balancing bellows of a pressure-balanced expansion joint.
The apparatus may further comprise the control apparatus further being operably configured, upon determination of the environmental condition to which the received first signal corresponds, to generate a third signal. A message transmittal apparatus may be operably configured to receive the third signal generated by the control apparatus, and in response thereto transmit a message to at least one designated recipient, at a location remote from the expansion joint, advising the recipient of the sensed environmental condition at the expansion joint.
The invention also comprises, in part, a method for monitoring pipeline expansion joint conditions, for use with a pressure-balanced expansion joint of the type incorporating a flow path bellows connecting first and second pipe ends in fluid communication with one another and at least first and second balancing bellows defining a variable enclosed volume, the method comprising the steps of:
providing at least one sensor operably configured to sense and respond to environmental conditions existing within a pipeline fluid flow through a pressure-balanced expansion joint;
the at least one sensor being further operably configured to generate a first signal corresponding to a particular value of at least one quantifiable characteristic of the environment existing within a pipeline fluid flow through a pressure-balanced expansion joint;
operably connecting a control apparatus to the sensor, the control apparatus being operably configured to receive the first signal corresponding to a particular value of at least one quantifiable characteristic of the environment existing within a pipeline fluid flow through a pressure-balanced expansion joint,
further operably configuring the control apparatus to compare the first signal received from the sensor with numerical values stored in memory corresponding to various potential environmental conditions of a pipeline fluid flow through a pressure-balanced expansion joint and determine the environmental condition to which the received first signal corresponds,
generating a second signal with the control apparatus, upon determination of the environmental condition to which the first signal corresponds;
providing a source of compressible medium;
operably connecting a flow control valve to at least the source of if compressible medium and the volume defined by first and second balancing bellows of a pressure-balanced expansion joint,
operably configuring the flow control valve to have at least two operating positions, a first operating position preventing flow through the flow control valve, and a second operating position permitting flow between the source of compressible medium, and the volume defined by first and second balancing bellows of a pressure-balanced expansion joint;
the second signal directing the flow control valve to one of the at least two operating positions, depending upon the environmental condition to which the first signal corresponds, to, in turn, add compressible medium, remove compressible medium and/or maintain the mass of compressible medium within the defined volume.
In the method of the present invention, the flow control valve may be provided with at least three positions, and the apparatus further comprising the step of operably connecting a fluid accumulator to the flow control valve, the third operating position of the flow control valve permitting flow between the fluid accumulator and the volume defined by first and second balancing bellows of a pressure-balanced expansion joint.
The method may further comprise the step of:
operably configuring the control apparatus to generate, upon determination of the environmental condition to which the received first signal corresponds, a third signal; and
providing a message transmittal apparatus operably configured to receive the third signal generated by the control apparatus, and in response thereto transmit a message to at least one designated recipient, at a location remote from the expansion joint, advising the recipient of the sensed environmental condition at the expansion joint.